Upgrade plans for the Subaru AO system

Abstract

A 36-elements curvature adaptive optics (AO) system has been operating on the Subaru telescope for about one and a half year. We achieved a Strehl ratio of 0.3 in the K-band, which is a rather smaller value than we expected. While we are investigating the discrepancy between the obtained performance and the simulated performance of the current AO system and we are also improving the current AO system in terms of the Strehl performance and the observing efficiency. Meanwhile we have started to plan a next generation of Subaru AO system. Two major upgrades are proposed in this paper. One is to increase the number of subapertures as much as possible. Practically, the number of subapertures lies between 100 and 200. The size of subaperture becomes half to one-third of that of the current system and we expected that the K-band Strehl ratio will improve to more than 0.6. The first light of the higher order curvature AO system is scheduled for 2004. Another upgrade plan is to use a laser guide star (LGS). A single LGS is projected at the sodium layer with an output power of 4 W. Conceptual designs for the laser system, beam relay system, laser launching telescope and control system have begun. The first test of launching laser from Subaru telescope will be in 2005.